The present invention relates to a photopolymerizable recording material in the form of a supply roll, in particular a dry photoresist material comprising a support film, a photopolymerizable layer and a covering film.
Materials of the above-mentioned type which are, for example, disclosed in U.S. Pat. No. 3,469,982 are extensively used in the production of printed circuits and in similar applications.
The thermoplastic photoresist layers of these materials must be adapted for dry transferring to another support material, for example a copper plate, with the application of pressure and usually also with heating. Therefore, the photoresist layer must be at least thermoplastically deformable, preferably even plastically deformable at ambient temperature, and it should have a particular tackiness. Materials showing these processing characteristics to an optimum degree present certain problems during storage and transport in the unexposed state, since their photoresist layers invariably tend to some cold flow which becomes apparent when the material is stored in the form of a roll. The photoresist layer then emerges between the film layers at the end faces of the roll and causes the wound-up layers to stick together. In an attempt to solve this problem, the composition of the photoresist layer, in particular the nature of the thermoplastic binder, has been modified to raise the flow temperature of the layer. This way of proceeding, which is described, for example, in German Offenlegungsschrift No. 23 63 806, is limited by the fact that the brittleness of the photo-crosslinked layer increases with the increased flow temperature of the unexposed layer, such that processing of the exposed material is rendered difficult.
Another solution to the problem is described in German Pat. No. 23 45 120. According to this patent, the edges of the photoresist layer are cured, so that the layer can no longer be squeezed out. The method has the disadvantage that, during processing of the respective material, light-sensitive substance is lost in the edge zones, since a particular safe distance must be allotted to ensure that any partly polymerized portions of the layer are excluded from the subsequent exposure and development. In addition, curing of the edge zones can give rise to a change in the relative adhesion of the photoresist layer to the support and covering films, which may produce the unwelcome effect of the layer adhering more firmly to the covering film than to the support film.